1. Technical Field
Example embodiments of the present invention relate to a method and apparatus for misfire detection for an internal combustion engine.
2. Related Art
Misfire detection is part of the requirements for any modern internal combustion engine, particularly for use in the automotive sector. The aim of misfire detection is to identify a misfire on any cylinder, including identification of the misfiring cylinder in a multi-cylinder engine.
There are various reasons for wishing to detect misfires, including a desire to identify misfires to avoid potential catalyst damage, and also to detect a potential deterioration in emissions performance of the internal combustion engine. An engine management system can be configured to set a fault status and, for example, to illuminate a malfunction indicator lamp in response to a certain rate of misfires (for example, a misfire per 1000 engine revolutions).
It is desirable to correctly identify all actual misfires as misfires if possible. It is also desirable to avoid identifying other events which do not actually represent misfires (due, for example, to engine operating conditions) as misfires in order to avoid an erroneous indication of a fault condition.
Indeed, different operating phases for an internal combustion engine can lead to noisy situations where the detection of a misfire compared to normal changes in the operating state of the internal combustion engine can be very difficult to detect.
The difficulty of detection arises at least in part due to the momentum of the moving parts within the engine, whereby a single misfire event may result in a very gradual decay in the speed of the engine. Such a gradual change in the speed as a result of a misfire may be barely discernable from a situation where there is a reduction in speed due, for example, to an additional load being placed on the engine.
Accordingly, example embodiment(s) of the present invention seeks to provide for improved misfire detection in an internal combustion engine, for example, in operating states of the internal combustion engine that place particular demands on misfire detection.